Safety attachment to power saws



July 1s, 1957 P. LEE SAFETYATTACHMENT To POWER sAws Filed Nov. 18, 1955Il. I'

INVENToR.- PATRICK LEE e Maf AGENT 0 lh .ull al s4 i t" 4.1. Il. ...000.l. 10.

United Sete ,Patient i 2,799,303 SAFETY ATTACHMENT TO POWERSAWS IPatrick Lee, Woodside, N. Y. Application November 18, 1955, Serial No.547,615

i 14 claims. (C1. 143-51) My present invention relates to a safetyattachment designed to prevent kickback in power saws, especially duringripping operations, and to facilitate the handling of boards in theimmediatevicinity of the saw blade.

In my prior U. S. patent application Serial No. 506,107, filed May 5,1955, issued April 5, 1957, as Patent No. 2,788,032, I have disclosed anattachment of/this general character having means for pushing a boardpast a rotating saw blade and for preventing the swirling blade fromhurling back the sawed-olf strip of wood toward the operator. Thegeneral object of my present invention is to provide a moresimpliedconstruction for an attachment of this type. y.

A more specific object of this invention is to provide an anti-kickbacksaw attachment adapted to engage the board being cut from above,preferably at a point located beyond the saw blade, in such manner as toinhibit any substantial backward movement of the board by frictionalcontact with the upper board surface, the attachment being arranged toaccommodate boards of various thicknesses without requiring individualadjustment.

Another more particular object of this invention is to provide, inassociation with an anti-kickback attachment as set forth above,conveniently operable means for releasing the attachment in order toprevent undesirable jamming of a board.

It is also an object of this invention to provide an attachment of theaforementioned character provided with anti-kickback and guiding meansadapted to engage a board without leaving objectionable traces thereon.

I have found, in accordance with my instant invention, that boards ofvarying thicknesses may be locked against undesirable unidirectionalmovement by means of a roller slidably guided (as by being journaled ina slot) along a path forming an acute angle, between about 30 and 60,with the (usually horizontal) supporting surface on which the board ismoving, the apex of the angle pointing in the forbidden direction ofmovement. Such roller, whose periphery may be roughened or knurled forbetter frictional contact with the wood, will ride freely on the boardwhen the latter moves in its permitted or forward direction but will actas a clamp upon the board when this movement is reversed.

Another feature of my invention resides in the provision of a simplemechanism for picking up the aforementioned roller and depositing itupon the upper surface of an approaching board. This mechanismcomprises, fundamentally, an elongated member pivotally supported on theroller axis, the end of said member facing the oncoming board forming anacute angle close to the supporting surface on which the board is movingand onto which the roller has dropped following the withdrawal of thepreceding board. The distance between the pointed end of the elongatedpick-up member and its pivotal axis must exceed not only the radius ofthe roller but also the thickness of the board; the leading edge of thehoard will then engage the pointed end of this member and, in rotatingthe member about its pivot,

2,799,303 Patented July 16, 1957 v v 2 cam this pivot upwardly along theinclined path of the roller which eventually reaches a position abovethe upper surface of the board and comes to rest on this surface uponthe continued forward movement of the board. The pick-up member ispreferably centrally symmetrical withrespect toits pivot whereby,following a rotation during the operation just described, its opposite,similarly pointed end will present itself to the next `following board.Advantageously, the pick-up member is in the form of a parallelogramwhose height is slightly less than` the diameter of the roller, whoseacute angle is at least approximately complementary to the angle of theguide slot or equivalent path-forming means, and whose two diagonals areeach longer than the roller diameter; the shorter edge of suchparallelogram approximately determines the maximum thickness of a boardto be accommodated by the mechanism.

My invention willbe described in greater detail with reference totheaccompanying drawing in which:

Fig. 1 is a perspective view of a saw table equipped with an attachmentembodying the invention;

Fig. 2 is a side elevational view, on a larger scale, of

the attachment itself in an inoperative position;

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2;

Fig. 4 is a sectional viewy taken on the line 4-4 of Fig. 2;

.Fig 5 is a view similar to Fig. 2 but showingthe attachment inoperative engagement with a board;

Fig. 6 is a top plan view of some of the elements shown in- Fig. 2; andf Fig. 7 is a detail view showing the pick-up mechanism of theattachment at an' intermediate stage between th positions of Figs. 2 and5. v

A conventional rotating saw blade 10, here shown as being of theso-called universal type with overhead support, is positioned above asaw table 11 provided with a fixed. outer guide rail 12 and anadjustable inner guide rail 13. A board about to be fed toward the blade10 is indicated at 14.

A carriage 15 straddles the rail 12 and is provided with dependingflanges having inturned edges 15' (Fig. 4) entering correspondingchannels 12' extending along the rear half of the rail. Carriage 15serves as a support for a pusher member 16 which is pivotally secured toa lug 17 thereof and is rigid with a stop plate 18 preventing thecounter-clockwise rotation of member 16 (as viewed in Figs. l, 2 and 5)beyond a vertically depending position illustrated in Fig. 5. Therounded underside 16 ofmember 16 enables the latter to ride freely andwithout scratching on the board 14 and other boards of differentthickness; when the board has been advanced so far that further directpushing by hand would be hazardous to the operator, carriage 15 isretracted by means of a handle 19 for a suliicient distance to allowmember 16 to drop behind the board whereupon a forward movement of thecarriage will feed the remainder of the board past the saw blade 10.Handle 19 is mounted in a safe position, e. g. extending laterally fromthe carriage as shown, so as to avoid any risk of the operators fingerscoming into Contact with the rotating blade.

The anti-kickback attachment proper comprises a guide plate 20 which isiixedly imbedded in a recess of guide rail 12, beyond the position ofsaw blade 10, and has the form of a parallelogram whose sides areinclined by about 45 to the surface of table 11. The two inclined sidesare provided, as best seen in Fig. 6, with integral flanges 20a, 20bdefining a slot 20c between them. Flange 20a extends above rail 12 forthe full height of plate 20 whereas flange 20b is somewhat foreshortenedand terminates flush with the upper surface of this rail. Plate 20 isalso provided with a slot 20d aligned with but narrower than slot 20c;both of these slots are parallel to the inclined edges of the plate. Asecond plate 21, slightly shorter and narrower than plate 26 but ofsimilar parallelogrammatic shape, is embraced by flanges 20a, 2Gb and isfurther guided by a pin 22, received in slot 20d, for slidingdisplacement relative to plate 20. A knurled roller 23 is rotatableabout a horizontal bolt 24 while passing through slot 20c and isfrictionallyengageable by a serrated edge of flange 20h, bolt 24secured, e. g. by a threaded connection, to plate 21. Normally, i. e. inthe absence of a board 14, plate 21 and roller 23 rest directly on table11 as illustrated in Figs. 2 and 3.

A pick-up member 2S, in the shape of a parallelogrammatic blade with 45flank inclination, is loosely pivoted on bolt 24 alongside roller 23whose diameter slightly exe ceeds the height of member 25, one of thelonger edges of this member being normally adjacent the upper surface oftable 11. Blade 25 when thus positioned has one of its two sharp corners25', 25 facing in the direction of the oncoming board 14. It will benoted that the shorter sides of blade 25 are of a length approximatelyequal to the height of board 14 but slightly less than the distance fromcorner 25 (or 25") to the axis of bolt 24, thus a littleV shorter thanhalf the longer diagonal of the parallelogram.

A horizontal shaft 26 is journaled in a bracket 27 rising from the rail12 adjacent plate 20. Shaft 26 carries a sectoral arm 28 having a milledor serrated periphery; this arm is adapted to engage a similarlyroughened edge of sliding plate 21 projecting above the foreshortenedflange 20b. A lever 29 secured to the other end of shaft 26 is pivotallylinked to a rod 30 which, via a pin 31, is coupled with a crank 32fastened to a stud 33. A trip member 34, received in a recess 35 at therear of rail 12, is secured to stud 33 so as to be fulcrumed thereonwhile being urged counter-clockwise (as viewed in Fig. 2) by acompression spring 36. The projecting end of trip member 34 is adaptedto be depressed, against the force of spring 36, by the carriage 15 whenthe latter is fully retracted beyond a normal limiting positionillustrated in Fig. l. The operation of the system illustrated in thedrawing is as follows:

As the board 14 is pushed forwardly past the blade 10, its leading edgecomes into contact with pointed corner 25 of pick-up blade 25, therebytending to rotate this blade in clockwise direction (as viewed in Fig.2) about bolt 24. Such rotation is at first prevented by the table 11,yet continued pressure of board 14 upon corner 25 causes the latter toco-act with the table surface in a camming action which drives the bolt24 up the slot 20c, thereby raising roller 23 and plate 21 from theirnormal bottom position as illustrated in Fig. 7.

Upon a further movement of board 14 the latter slips under the roller 23and the member 25, having gone through a rotation of 180, comes to reston top of the board as illustrated in Fig. 5. In this position the boardis effectively locked against reverse movement since the yroller 23,frictionally engaging the board, cannot move backwards (to the right inFig. without also frictionally engaging the roughened edge of slot 20cformed by flange Ztlb; any backward pressure upon board 14 will thus beresisted by a clamping action by the inclined ange 2Gb which causesboard 14 to become tightly wedged between roller 23 and table 11.

When the rear edge of board 1.4 passes the pusher member 16 (carriage 15being in its retracted position shown in Fig. l), the operator takes hisright hand off the board and grips the handle 19 to complete the cuttingoperation. As the carriage reaches the forward end of its travel, pusher16 has driven the board past blade 10; the same process is now repeatedwith a new board which drives the sawed-off strip of board 14 out fromunder roller 23 so that this strip may be taken oft the table. If board14 is not to be followed by another, the strip may be 4 pulled out orpushed out by hand after the saw blade 10 hasbeen stopped. Roller 23 andplate 21 thereupon return by gravity to their normal position, thisbeing facilitated by making slot 20c slightly wider than bolt 24 andallowing plate 21 a certain play between flanges 20a, Zlib.

If the blade 10 should become jammed in the wood of a board being cut,the operator simply retracts carriage 15 beyond the position of Fig. lso that trip member 34 is depressed. This clockwise movement of the tripmember (as viewed in Fig. 2) causes rod 30 to move forwardly (to theleft in Figs. 2 and 5) and imparts a similar clockwise movement to arm28 whose roughened periphery makes tangential Contact With the equallyroughened exposed ank of plate 21, thereby lifting up this plate andraising the roller 23 from the board. It will be noted that this actionof the release mechanism 28, 30, 34 is independent of the position ofplate 21 within the range of thicknesses of the boards to be cut, owingto the ability of arm 28 to engage plate 21 anywhere along the length ofits ank.

The invention is, of course, not limited to the specific embodimentdescribed and illustrated but may be realized in a variety ofmodifications and adaptations without departing from the spirit andscope of the appended claims. Furthermore, it will be understood thatthe principles herein disclosed are equally applicable to bench saws inwhich the saw blade projects upwardly from the table. Finally, thesystem described remains operative even if the guide rail 12 isdisplaced from its position parallel to the blade 10 to enable thetaking of miter cuts.

I claim:

l. In a power saw with circular blade, in combination, a table adaptedto support a board to be cut by said blade, a roller above said tablerotatable about an axis parallel to said table, guide means supportingsaid roller for movement along a path forming an acute angle with saidtable, the apex of said angle pointing in a direction opposite to thenormal direction of movement of said board, and pick-up means secured tosaid roller, said pick-up means comprising an elongated member pivotableabout the roller axis, said member having a first edge adapted to assumea position adjacent and substantially parallel to said table and asecond edge forming with said first edge an acute angle pointing in saidopposite direction upon assumption of said position by said first edge.

2. The combination according to claim l, wherein said guide meanscomprises a plate perpendicular to said table and provided with a slot,said roller having a shaft received in said slot.

3. The combination according to claim 1, wherein the angle between saidfirst and second edges is approximately complementary to the anglebetween said path and said table.

4. The combination according to claim 3, wherein both of said, anglesare between approximately 30 and 60.

5. The combination according to claim 4, wherein both of said angles aresubstantially equal to 6. A safety attachment for power saws comprising,in combination with a table and a saw blade positioned to cut a boardadvancing on said table, a rail on said table for guiding said boardtoward said blade, a carriage slidable on said rail, and pusher means onsaid carriage adapted to engage the rear edge of said board, said pushermeans comprising a swingable arm positioned alongside said carriage andpivotally mounted thereon, said arm being displaceable between anelevated position above the upper surface of said board and a dependingposition, and abutment means rigid with said arm and overlying saidrail, said abutment means coming to rest on said rail in said dependingposition, thereby preventing the latter from swinging beyond saiddepending position in a direction away from said blade.

7. An attachment according to claim 6, wherein said Aarm lis providedwith a .curved underside adapted to lride 5 on the upper surface of saidboard in said elevated position.

8. An anti-kickback device i" or a power saw with circular, blade,comprising a supporting element and a supported element engaging eachother for relative sliding movement along an inclined path upon apositioning of said supporting element on a horizontal bearing surface,said supported element including a horizontal shaft, a roller journaledon said shaft and a parallelogrammatic pick-up member centrally pivotedon said shaft adjacent said roller, said member having one of its sharpcorners facing toward the apex of the angle enclosed between said pathand said surface upon a horizontal positioning of one of the edges ofsaid member.

9. A device according to claim 8, wherein said roller is provided with aroughened periphery.

10. A device according to claim 9, wherein said supporting element isprovided with a roughened edge frictionally engageable by said rollerupon the latter being urged in a direction toward said apex.

11. A device according to claim 8, wherein the height of said membernormal to its longer sides is less than the diameter of said roller,both diagonals of said member being greater than said diameter.

12. A device according to claim 1l, wherein the angle between said pathand said surface and the angles at the sharp corners of said member areeach of about 45.

13. A device according to claim 8, wherein said supported element isprovided with a roughened edge, further comprising a release mechanismincluding a pivoted element positioned for engagement with saidroughened edge and operating means for actuating said pivoted elementfrom a distance for lifting said supported element relatively to saidsupporting element.

14, In a power saw with circular blade, in combination, a table adaptedto support a board to be cut by said blade, a roller above said tablepositioned in the vicinity of said blade and rotatable about an axisparallel to said table, guide means supporting said roller for movementalong a path forming an acute angle with said table, the apex of saidangle pointing in a direction opposite to the normal direction ofmovement of said board, a release member remote from said blade,transmission means operatively linking said release lmember with saidroller for lifting the latter oli said board, a guide rail extending`above said table past said blade, a carriage slidable on said rail andpusher means on said carriage for advancing said board past said blade,said carriage being operativelyengageable with said release member forlifting said roller oli said board.

References Cited in the le of this patent UNITED STATES PATENTS 604,661Johnston et al May 24, 1898 1,072,401 Ofutt Sept. 2, 1913 1,074,198Phillips Sept. 30, 1913 1,135,168 Edman Apr. 13, 1915 1,430,983 GranbergOct. 3, 1922 2,696,852 Dunton Dec. 14, 1954 2,731,049 Akin Jan. 17, 19562,788,032 Lee Apr. 9, 1957 FOREIGN PATENTS 185,254 Great Britain Sept.7, 1922

